1. Field of the Invention
The present invention relates to a process cartridge attachable/detachable to/from an apparatus main body, and an electrophotographic image forming apparatus. The process cartridge is configured such that an electrophotographic photoreceptor and a development device working on the electrophotographic photoreceptor are integrated in a cartridge, which is attachable/detachable to/from the electrophotographic image forming apparatus main body. The development device has a development roller and is configured to visualize an electrostatic latent image formed on the electrophotographic photoreceptor by the development roller by use of a development agent. Further, the electrophotographic image forming apparatus is configured to form an image on a recording medium by use of an electrophotographic image forming system. Examples of the electrophotographic image forming apparatus include electrophotographic copying machine, electrophotographic printer (such as a light-emitting diode (LED) printer or laser beam printer), facsimile, word processor, and the like.
2. Description of the Related Art
A process cartridge includes a photosensitive unit having a photosensitive drum, and a development unit having a development roller for developing an electrostatic latent image formed on the photosensitive drum. The photosensitive unit and the development unit are coupled with each other at both ends in a direction parallel to a rotational center axis of the photosensitive drum. An electrophotographic image forming apparatus in a non-contact development system is configured such that a slight gap is formed between the surface of the photosensitive drum and the surface of the development roller. In this case, for example, rollers (interval holding members) each having a slightly larger diameter than the development roller are provided at both ends of the development roller and the pair of rollers always contacts the photosensitive drum. Thereby, a distance between the surface of the drum and the surface of the development roller can be kept constant. In such a technique, the photosensitive unit and the development unit are typically coupled at one end to give a certain degree of freedom to their motions in the direction parallel to the rotational center axis line to always bring the pair of rollers into contact with the photosensitive drum. Thereby, even if a dimensional error is present in various members, the development unit gives a force to the photosensitive unit by using a force giving member such as spring, so that the pair of rollers can always contact the photosensitive drum. There is known a technique for coupling the photosensitive unit and the development unit by a link member rotatably coupled to both of them to couple the units giving a certain degree of freedom to their motions (see Japanese Patent Application Laid-Open No. 2013-20233 Publication).
However, the process cartridge with the above structure has a problem that if the process cartridge packaged in a box is dropped during transportation, the development roller and the photosensitive drum collide with each other and the surface of the photosensitive drum is damaged. That is, the photosensitive drum has a large diameter and is light while the development roller has a smaller diameter and is heavy due to a magnet disposed therein. Thus, the development roller is elongate and heavy, and more flexible than the photosensitive drum. Therefore, when subjected to an impact, the development roller largely bends and collides with the surface of the photosensitive drum. There is known a technique for providing a protective sheet between the photosensitive drum and the development roller to address such a problem (see Japanese Patent Application Laid-Open No. 2000-019800 Publication). Further, there is known, as other solution, a method for enhancing a performance of a buffer material to alleviate an impact on the process cartridge during transportation.
However, the technique for providing a protective sheet needs to add a protective sheet only for the case of transportation, which remarkably increases the number of components and needs a step of incorporating a protective sheet into the process cartridge during its assembly. In order to enhance a performance of the buffer material, a highly-functional buffer material needs to be employed or a size of the buffer material needs to be increased, which causes an increase in cost.
It is required to restrict a collision between the development roller and the photosensitive drum while preventing an increase in cost without increasing the number of components.